The disclosure relates to a laser unit and an extreme ultraviolet light generating system to generate extreme ultraviolet (EUV) light, based on pulsed laser light outputted from the laser unit.
In recent years, miniaturization of a transcription pattern of an optical lithography in a semiconductor process is drastically progressing with the development in fining of the semiconductor process. In the next generation, microfabrication on the order of 70 nm to 45 nm, and further microfabrication on the order of 32 nm or less are bound to be required. To meet such requirement for the microfabrication on the order of, for example, 32 nm or less, development is anticipated of an exposure apparatus that includes a combination of a reduced projection reflective optics and an extreme ultraviolet light generating apparatus that generates extreme ultraviolet (EUV) light with a wavelength of about 13 nm. For example, reference is made to Japanese Unexamined Patent Application Publication (Published Japanese Translation of PCT Application) No. JP2013-502059, and U.S. Patent Application Publication No. 2012/0147349.
As the EUV light generating apparatus, three kinds of apparatuses, laser produced plasma (LPP) apparatus using plasma generated by irradiation of a target substance with laser light, a discharge produced plasma (DPP) apparatus using plasma generated by electric discharge, and a synchrotron radiation (SR) apparatus using orbital radiation light have been proposed.